It is time for us to be honest: the reason Psi has not had a release in the past year and a half is because we have secretly been working on one of the most controversial and least implemented features in the Jabber world: XEP-0076 (Malicious Stanzas). We have allocated two full-time developers for achieving this: Machekku has done the groundbreaking work, implementing the main processing loop, statistic gathering, and user interfaces for this type of stanzas, whereas I have been concentrating mostly on backend issues. Although our work is still in a highly experimental stage, we decided to release the full source code in order to get useful feedback from the community. Besides a Psi implementation, we also provide an Openfire server-side implementation for malicious stanza tagging as an extension of the content filter, targeted at fixing non-XEP-0076-compliant behavior of entities.
You can find Machekku's and my Psi work here and here respectively. Apply these patches to a clean development version of Psi. In order to use this work, please modify the <evil> section of your options.xml accordingly. XEP-0076 statistics can be found in the options dialog, in a separate tab.
The patch against the latest development version of Openfire can be found here. This will add an extra checkbox to the content filter pane, allowing messages to be tagged as malicious.